The time critical applications like public switched telephone network (PSTN calls are affected when the network re-converges due to faults. Fast Reroute (FRR) is a technology used in networking to ensure the service availability is assured. FRR is the technology proposed by Internet Engineering Task Force (IETF) for local protection of a MPLS network. The technology provides fast protection switching capability for a Label Switched Path (LSP) by means of traffic engineering capability of the MPLS.
In MPLS, a connection referred to as a label switched path (LSP) is established between two end points and packets are transported along the LSP using label switching. Various signaling protocols may be used to set up and manage LSPs. Examples include Resource Reservation Protocol (RSVP) and its various extensions such as RSVP-TE for traffic engineering, and others. RSVP-TE provides a mechanism for reserving resources for LSPs. Resource Reservation Protocol-Traffic Engineering is an extension of the resource reservation protocol (RSVP) for traffic engineering. It supports the reservation of resources across an IP network.
Routers that are capable of performing label-based switching according to the MPLS protocol are referred to as label switch routers (LSRs). The entry and exit points of an MPLS network are called label edge routers (LERs). The entry router is referred to as ingress LER and the exit router as an egress LER. LSPs are unidirectional tunnels that enable a packet to be label switched through the MPLS network from ingress LER to an egress LER. The flow of packets along an LSP may be disrupted by various network events such as failure of an interface or link along a path traversed by an LSP, failure of a node (e.g., a router) in the LSP path, reduction in bandwidth associated with a link traversed by the LSP, a priority-related event such as when a new high priority LSP comes up and there is bandwidth contention or a change in priority of an existing LSP, which may result lower priority LSPs to get preempted, and others. To protect against potential data losses caused by such disruptions, a backup LSP may be provisioned for an LSP (referred to as the primary LSP to differentiate it from the backup LSP). The backup LSP provides an alternative path for forwarding packets around a failure point in the primary LSP. Since the primary LSP is “protected” by its corresponding backup LSP, the primary LSP is referred to as a protected LSP.
The Fast ReRoute (FRR) extension to RSVP-TE provides a mechanism for establishing backup LSPs for protecting primary LSPs. The protected LSP is also referred to as an FRR-enabled LSP. When a network event occurs that affects a protected LSP, the packet traffic is locally redirected along the backup LSP in a manner that circumvents the failure point in the protected LSP. When a router starts redirecting data along a backup LSP for a protected LSP, the protected LSP is referred to as being failed over to the backup LSP. FRR enables RSVP to set up a backup LSP to protect an LSP so that in the event of a network failure (e.g., link/node failure), the data traffic from the protected LSP can be switched to the backup LSP to minimize any traffic loss. RSVP-TE on the local device, such as router, associates the working or current LSPs to a FRR (facility backup) LSP based on local FRR configuration and RSVP-TE signaling messages (such as RSVP path and resv messages) exchange. The path message for the LSP to be protected specifies the desired protection, and the resv message propagated towards ingress of the LSP specifies the level of protection available along the path.
The software-defined networking (SDN) is one of the recent approaches to computer networking that allows network administrators to manage network services through abstraction of higher-level functionality. This is done by decoupling the system that makes decisions about where traffic is sent (the control plane) from the underlying systems that forward traffic to the selected destination. Generally, the SDN networks are path computation element (PCE)/path computation client (PCC) managed. The PCE is a system component, application, or network node that is capable of determining and finding a suitable route for conveying data between a source and a destination. The PCE device can be a router, a COTS server, part of the OSS, or a virtualized entity running in a cloud. When a network node needs a path for an LSP, it makes a request to the PCE using the PCE protocol (PCEP). The PCE has access to topology information for the entire network and uses this in path computations.
However, the RSVP-TE does not ensure a central control of associating working and FRR (facility backup) LSPs at a particular node. Also, in SDN environment where the LSPs are PCE initiated, and in PCE methods where RSVP signaling for LSPs is completely removed, cannot use the existing FRR mechanisms of RSVP-TE. Further, in case of PCE managed SDN network, there is no mechanism for either PCC or PCE to associate the working/current LSPs (i.e., LSPs to be protected) to FRR LSP, and switch the traffic to FRR LSP (i.e., put FRR LSP in use) upon resource (node/link) failure, due to which the status of FRR LSP in use is not updated with the PCE. Furthermore, when the working LSPs and FRR LSP are delegated to PCE, the PCE does not have the information to group the working LSPs and FRR LSPs so as to ensure the protection of working LSP. Also, when the working LSP is initiated by PCE, there is no means for PCE to initiate the FRR LSP and protect the working LSPs.